4. The cross pollination and fertilization can also be achieved easily.

5. The flowers are bisexual and hermaphrodite.

Mendel made sure that his plants were pure bred for the single trait he wanted to study. He did this by letting the plant self pollinate for many generations. Then Mendel performed hundreds of crosses. Seven pairs of contrasting characters were chosen for his study.

For cross pollination, garden pea, being self fertilizing plant, anthers have to be removed before maturity. This operation of removal of anthers is called emasculation. The stigma is protected against any undesired, foreign pollen with the help of a bag.

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Pollen grains from desired plant are collected from male parent and dusted on stigma of flower in female parent. At the time of cross pollination, the pollen should be mature and stigma should be receptive.

Although Mendel studied the inheritance of seven different pairs of contrasting characters in garden pea (Pisum sativum), but he considered to pea plants with alternate characters by artificial pollination with technique discussed above. He pooled the data of many similar crosses, analysed the results and found that traits appeared in progeny in definite ratio.

Table 5.3. Contrasting characters of Pisum sativum that were studied by Mendel.

1. Tall vine (6-7 ft.).

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2. Axial flowers and pods.

3. Light or dark green pods.

4. Non-constricted or full pods.

5. Grey seed coat.

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6. Yellow endosperm.

7. Round seeds.

Dwarf vine (% -m ft.).

Terminal flowers and pods

Yellow pods.

Constricted pods.

White seed coat.

Green endosperm.

Wrinkled seeds.

What did Mendel do?

Mendel performed his experiments in three stages. First, he made sure that his plants were pure bred (14 varieties for 7 pairs of contrasting characters) (Table 5.3). He did this by letting the plants fertilize themselves to eliminate any offspring that was not true to the form of the trait. It was thus made sure that offspring of each generation were all like the parent plant. These true breeding plants constituted the parents(P).

Second stage was to hybridise the plants. He made several crosses by dusting the pollen of one kind on stigmas of plants of another kind. For instance, he pollinated plants from a strain whose seeds were always round, with pollen from a strain whose seeds were always wrinkled.

Such offspring of different parents with contrasting characters form the first filial generation or F1 generation. Mendel further made reciprocal crosses. Third stage of Mendel’s experiments was to let the F1 plants pollinate themselves. Plants thus produced were called second filial or F2 generation. Similarly F3, F4 etc. were also obtained.